reloc.c revision 1.60
1 /* $NetBSD: reloc.c,v 1.60 2002/09/05 20:08:14 mycroft Exp $ */ 2 3 /* 4 * Copyright 1996 John D. Polstra. 5 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by John Polstra. 19 * 4. The name of the author may not be used to endorse or promote products 20 * derived from this software without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 /* 35 * Dynamic linker for ELF. 36 * 37 * John Polstra <jdp (at) polstra.com>. 38 */ 39 40 #include <err.h> 41 #include <errno.h> 42 #include <fcntl.h> 43 #include <stdarg.h> 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include <unistd.h> 48 #include <sys/types.h> 49 #include <sys/mman.h> 50 #include <dirent.h> 51 52 #include "debug.h" 53 #include "rtld.h" 54 55 #ifndef RTLD_INHIBIT_COPY_RELOCS 56 static int _rtld_do_copy_relocation __P((const Obj_Entry *, const Elf_Rela *, 57 bool)); 58 59 /* 60 * XXX: These don't work for the alpha and i386; don't know about powerpc 61 * The alpha and the i386 avoid the problem by compiling everything PIC. 62 * These relocation are supposed to be writing the address of the 63 * function to be called on the bss.rel or bss.rela segment, but: 64 * - st_size == 0 65 * - on the i386 at least the call instruction is a direct call 66 * not an indirect call. 67 */ 68 static int 69 _rtld_do_copy_relocation(dstobj, rela, dodebug) 70 const Obj_Entry *dstobj; 71 const Elf_Rela *rela; 72 bool dodebug; 73 { 74 void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset); 75 const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info); 76 const char *name = dstobj->strtab + dstsym->st_name; 77 unsigned long hash = _rtld_elf_hash(name); 78 size_t size = dstsym->st_size; 79 const void *srcaddr; 80 const Elf_Sym *srcsym = NULL; 81 Obj_Entry *srcobj; 82 83 for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) 84 if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, 85 false)) != NULL) 86 break; 87 88 if (srcobj == NULL) { 89 _rtld_error("Undefined symbol \"%s\" referenced from COPY" 90 " relocation in %s", name, dstobj->path); 91 return (-1); 92 } 93 srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value); 94 (void)memcpy(dstaddr, srcaddr, size); 95 rdbg(dodebug, ("COPY %s %s %s --> src=%p dst=%p *dst= %p size %ld", 96 dstobj->path, srcobj->path, name, (void *)srcaddr, 97 (void *)dstaddr, (void *)*(long *)dstaddr, (long)size)); 98 return (0); 99 } 100 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 101 102 103 /* 104 * Process the special R_xxx_COPY relocations in the main program. These 105 * copy data from a shared object into a region in the main program's BSS 106 * segment. 107 * 108 * Returns 0 on success, -1 on failure. 109 */ 110 int 111 _rtld_do_copy_relocations(dstobj, dodebug) 112 const Obj_Entry *dstobj; 113 bool dodebug; 114 { 115 #ifndef RTLD_INHIBIT_COPY_RELOCS 116 117 /* COPY relocations are invalid elsewhere */ 118 assert(dstobj->mainprog); 119 120 if (dstobj->rel != NULL) { 121 const Elf_Rel *rel; 122 for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) { 123 if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) { 124 Elf_Rela ourrela; 125 ourrela.r_info = rel->r_info; 126 ourrela.r_offset = rel->r_offset; 127 ourrela.r_addend = 0; 128 if (_rtld_do_copy_relocation(dstobj, 129 &ourrela, dodebug) < 0) 130 return (-1); 131 } 132 } 133 } 134 if (dstobj->rela != NULL) { 135 const Elf_Rela *rela; 136 for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) { 137 if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) { 138 if (_rtld_do_copy_relocation(dstobj, rela, 139 dodebug) < 0) 140 return (-1); 141 } 142 } 143 } 144 #endif /* RTLD_INHIBIT_COPY_RELOCS */ 145 146 return (0); 147 } 148 149 150 #if !defined(__sparc__) && !defined(__x86_64__) && !defined(__mips__) 151 152 #if !defined(__powerpc__) && !defined(__hppa__) 153 154 int 155 _rtld_relocate_plt_object(obj, rela, addrp, bind_now, dodebug) 156 Obj_Entry *obj; 157 const Elf_Rela *rela; 158 caddr_t *addrp; 159 bool bind_now; 160 bool dodebug; 161 { 162 Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset); 163 Elf_Addr new_value; 164 165 /* Fully resolve procedure addresses now */ 166 167 if (bind_now || obj->pltgot == NULL) { 168 const Elf_Sym *def; 169 const Obj_Entry *defobj; 170 171 #if !defined(__arm__) 172 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT)); 173 #else 174 assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JUMP_SLOT)); 175 #endif 176 177 def = _rtld_find_symdef(rela->r_info, obj, &defobj, true); 178 if (def == NULL) 179 return -1; 180 181 new_value = (Elf_Addr)(defobj->relocbase + def->st_value); 182 #if defined(__sh__) || defined(__vax__) 183 new_value += rela->r_addend; 184 #endif 185 rdbg(dodebug, ("bind now %d/fixup in %s --> old=%p new=%p", 186 (int)bind_now, 187 defobj->strtab + def->st_name, 188 (void *)*where, (void *)new_value)); 189 } else if (!obj->mainprog) { 190 /* Just relocate the GOT slots pointing into the PLT */ 191 new_value = *where + (Elf_Addr)(obj->relocbase); 192 rdbg(dodebug, ("fixup !main in %s --> %p", obj->path, 193 (void *)*where)); 194 } else { 195 return 0; 196 } 197 /* 198 * Since this page is probably copy-on-write, let's not write 199 * it unless we really really have to. 200 */ 201 if (*where != new_value) 202 *where = new_value; 203 if (addrp != NULL) { 204 *addrp = *(caddr_t *)(obj->relocbase + rela->r_offset); 205 #if defined(__vax__) 206 *addrp -= rela->r_addend; 207 #endif 208 } 209 return 0; 210 } 211 212 #endif /* __powerpc__ || __hppa__ */ 213 214 #endif /* __sparc__ || __x86_64__ || __mips__ */ 215 216 caddr_t 217 _rtld_bind(obj, reloff) 218 Obj_Entry *obj; 219 Elf_Word reloff; 220 { 221 const Elf_Rela *rela; 222 Elf_Rela ourrela; 223 caddr_t addr; 224 225 if (obj->pltrel != NULL) { 226 const Elf_Rel *rel; 227 228 rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff); 229 ourrela.r_info = rel->r_info; 230 ourrela.r_offset = rel->r_offset; 231 ourrela.r_addend = 0; 232 rela = &ourrela; 233 } else { 234 rela = (const Elf_Rela *)((caddr_t) obj->pltrela + reloff); 235 #ifdef __sparc64__ 236 if (ELF_R_TYPE(obj->pltrela->r_info) == R_TYPE(JMP_SLOT)) { 237 /* 238 * XXXX 239 * 240 * The first four PLT entries are reserved. There 241 * is some disagreement whether they should have 242 * associated relocation entries. Both the SPARC 243 * 32-bit and 64-bit ELF specifications say that 244 * they should have relocation entries, but the 245 * 32-bit SPARC binutils do not generate them, 246 * and now the 64-bit SPARC binutils have stopped 247 * generating them too. 248 * 249 * So, to provide binary compatibility, we will 250 * check the first entry, if it is reserved it 251 * should not be of the type JMP_SLOT. If it 252 * is JMP_SLOT, then the 4 reserved entries were 253 * not generated and our index is 4 entries too far. 254 */ 255 rela -= 4; 256 } 257 #endif 258 } 259 260 if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0) 261 _rtld_die(); 262 263 return addr; 264 } 265 266 /* 267 * Relocate newly-loaded shared objects. The argument is a pointer to 268 * the Obj_Entry for the first such object. All objects from the first 269 * to the end of the list of objects are relocated. Returns 0 on success, 270 * or -1 on failure. 271 */ 272 int 273 _rtld_relocate_objects(first, bind_now, dodebug) 274 Obj_Entry *first; 275 bool bind_now; 276 bool dodebug; 277 { 278 Obj_Entry *obj; 279 int ok = 1; 280 281 for (obj = first; obj != NULL; obj = obj->next) { 282 if (obj->nbuckets == 0 || obj->nchains == 0 || 283 obj->buckets == NULL || obj->symtab == NULL || 284 obj->strtab == NULL) { 285 _rtld_error("%s: Shared object has no run-time" 286 " symbol table", obj->path); 287 return -1; 288 } 289 rdbg(dodebug, (" relocating %s (%ld/%ld rel/rela, " 290 "%ld/%ld plt rel/rela)", 291 obj->path, 292 (long)(obj->rellim - obj->rel), 293 (long)(obj->relalim - obj->rela), 294 (long)(obj->pltrellim - obj->pltrel), 295 (long)(obj->pltrelalim - obj->pltrela))); 296 297 if (obj->textrel) { 298 /* 299 * There are relocations to the write-protected text 300 * segment. 301 */ 302 if (mprotect(obj->mapbase, obj->textsize, 303 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { 304 _rtld_error("%s: Cannot write-enable text " 305 "segment: %s", obj->path, xstrerror(errno)); 306 return -1; 307 } 308 } 309 if (_rtld_relocate_nonplt_objects(obj, dodebug) < 0) 310 ok = 0; 311 if (obj->textrel) { /* Re-protected the text segment. */ 312 if (mprotect(obj->mapbase, obj->textsize, 313 PROT_READ | PROT_EXEC) == -1) { 314 _rtld_error("%s: Cannot write-protect text " 315 "segment: %s", obj->path, xstrerror(errno)); 316 return -1; 317 } 318 } 319 /* Process the PLT relocations. */ 320 if (obj->pltrel != NULL) { 321 const Elf_Rel *rel; 322 for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) { 323 Elf_Rela ourrela; 324 ourrela.r_info = rel->r_info; 325 ourrela.r_offset = rel->r_offset; 326 ourrela.r_addend = 327 *(Elf_Word *)(obj->relocbase + 328 rel->r_offset); 329 if (_rtld_relocate_plt_object(obj, &ourrela, 330 NULL, bind_now, dodebug) < 0) 331 ok = 0; 332 } 333 } 334 if (obj->pltrela != NULL) { 335 const Elf_Rela *rela; 336 for (rela = obj->pltrela; rela < obj->pltrelalim; 337 ++rela) { 338 #ifdef __sparc64__ 339 if (ELF_R_TYPE(rela->r_info) != 340 R_TYPE(JMP_SLOT)) { 341 /* 342 * XXXX 343 * 344 * The first four PLT entries are 345 * reserved. There is some 346 * disagreement whether they should 347 * have associated relocation 348 * entries. Both the SPARC 32-bit 349 * and 64-bit ELF specifications say 350 * that they should have relocation 351 * entries, but the 32-bit SPARC 352 * binutils do not generate them, 353 * and now the 64-bit SPARC binutils 354 * have stopped generating them too. 355 * 356 * To provide binary compatibility, we 357 * will skip any entries that are not 358 * of type JMP_SLOT. 359 */ 360 continue; 361 } 362 #endif 363 if (_rtld_relocate_plt_object(obj, rela, 364 NULL, bind_now, dodebug) < 0) 365 ok = 0; 366 } 367 } 368 if (!ok) 369 return -1; 370 371 372 /* Set some sanity-checking numbers in the Obj_Entry. */ 373 obj->magic = RTLD_MAGIC; 374 obj->version = RTLD_VERSION; 375 376 /* Fill in the dynamic linker entry points. */ 377 obj->dlopen = _rtld_dlopen; 378 obj->dlsym = _rtld_dlsym; 379 obj->dlerror = _rtld_dlerror; 380 obj->dlclose = _rtld_dlclose; 381 obj->dladdr = _rtld_dladdr; 382 383 /* Set the special PLTGOT entries. */ 384 if (obj->pltgot != NULL) 385 _rtld_setup_pltgot(obj); 386 } 387 388 return 0; 389 } 390
Indexes created Tue Sep 30 07:10:03 GMT 2025